scan or source a text file into a list

I've ported somebody else's rather cumbersome Matlab model to R for
colleagues that want a free build of the model with the same type of I/O.

The Matlab model reads a text file with the initial parameters specified as:
I think I would be tempted to try out read.dcf() for this, which returns a 
character matrix of field values in named columns, from which values cast 
to numeric:
system("cat tmp/Params.dcf")
nYears: 50
year0: 1970
fnr: 0.30
qe: 0.040
x <- read.dcf("tmp/Params.dcf")
x
nYears year0  fnr    qe     
[1,] "50"   "1970" "0.30" "0.040"
str(x)
chr [1, 1:4] "50" "1970" "0.30" "0.040"
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:4] "nYears" "year0" "fnr" "qe"

Since you will know the mode you need, you could read the same-mode fields 
together and cast them:
x <- read.dcf("tmp/Params.dcf", fields=c("nYears", "year0"))
mode(x) <- "integer"
x
nYears year0
[1,]     50  1970

and make x a data frame if say x$nYears is needed, which gets to list:
as.list(data.frame(x))
$nYears
[1] 50

$year0
[1] 1970

and c() of the different mode lists to make inputParamList. I think 
treating everything as numeric may be enough, and the DCF format is 
flexible.

Roger
C:\Data\Carluc\Rport>more Params.R
# Number of years to simulate
nYears = 50;
# Initial year for graphing purposes
year0 = 1970;
# NPP/GPP ratio (cpp0 unitless)
fnr = 0.30;
# Quantum efficency
qe  = 0.040;

That is, there are four input variables (for this run - there can be many
more) written in a way that R can understand them. In R, I can have the
model source the parameter text file easily enough and have the objects in
the workspace. The model function in R takes a list at runtime. How can I
have R read that file and put the contents into the list I need?

E.g.,
rm(list = ls())
source("Params.R")
ls()
[1] "fnr"    "nYears" "qe"     "year0"
fnr
[1] 0.3
nYears
[1] 50
foo.list <- list(fnr = fnr, nYears = nYears)

foo.list
$fnr
[1] 0.3

$nYears
[1] 50

The model is then run with
CarlucR(inputParamList = foo.list, ...)
I can't build inputParamList "by hand" as above because the number of
initial parameters changes with the model run and this runs in a wrapper.

Any thoughts? Some combination of paste with scan or parse?
-Andy

version
         _
platform i386-pc-mingw32
arch     i386
os       mingw32
system   i386, mingw32
status
major    2
minor    0.0
year     2004
month    10
day      04
language R

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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no

scan or source a text file into a list

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